CN114072320A

CN114072320A - Steering device

Info

Publication number: CN114072320A
Application number: CN202080049410.9A
Authority: CN
Inventors: 高桥和树
Original assignee: KYB Corp
Current assignee: KYB Corp
Priority date: 2019-07-12
Filing date: 2020-03-02
Publication date: 2022-02-18
Anticipated expiration: 2040-03-02
Also published as: CN114072320B; JP2021014210A; JP7344027B2; WO2021009964A1; US20220348255A1

Abstract

A steering device (100) is provided with: a rack shaft (30) that changes the direction of a wheel (1); bushings (35, 36) that slidably support the rack shaft (30); tie rods (41a, 41b) coupled to the rack shaft (30); and sheaths (37a, 37b) that cover the connection sections between the rack shaft (30) and the tie rods (41a, 41 b). A protrusion (35c) is formed on one of the bushings (35, 36) and the rack housing (31), and a restriction groove (32b) into which the protrusion (35c) is inserted is formed on the other. The space in the first sheath (37a) and the space in the second sheath (37b) are always in communication via the restriction groove (32 b).

Description

Steering device

Technical Field

The present invention relates to a steering device.

Background

In japanese patent laid-open publication JP2009-227030a, a steering device is disclosed, which is provided with: a rack shaft that changes the direction of the wheels by transmitting a steering force; a housing that houses the rack shaft; a bushing provided in the housing and supporting the rack shaft to be slidable; a pull rod connected to the rack shaft in a freely swingable manner; and a sheath covering a coupling portion between the rack shaft and the tie rod. In this steering apparatus, when the rack shaft reciprocates, the space inside each sheath expands and contracts in accordance with the operation.

Disclosure of Invention

In the steering device described in japanese patent laid-open No. JP2009-227030, since grease and lubricating oil exist between the bush and the housing and between the bush and the rack shaft, there is almost no gap through which air can flow. Therefore, the space inside each jacket is substantially sealed. When the space in the sheath is sealed in this way, even if the sheath expands and contracts in accordance with the reciprocating movement of the rack shaft, air cannot enter and exit the space in the sheath, and therefore the sheath made of rubber or resin may be deformed extremely and damaged.

The purpose of the present invention is to suppress deformation of a sheath.

According to one aspect of the present invention, a steering device includes: a steering shaft that changes a direction of a wheel by being transmitted with a steering force; a housing that houses the steered shaft; a bush provided in the housing and supporting the steering shaft to be slidable; a first link and a second link that are connected to the steered shaft so as to be able to freely swing; a first sheath that is provided in the housing and covers a coupling portion between the steered shaft and the first link; and a second sheath that is provided in the housing and covers a connection portion between the steered shaft and the second link, wherein a protruding portion that protrudes toward the other is formed on one of the bush and the housing, a restriction groove into which the protruding portion is inserted is formed on the other in an axial direction of the steered shaft, and a space in the first sheath and a space in the second sheath are always communicated with each other via the restriction groove.

Drawings

Fig. 1 is a configuration diagram of a steering device according to an embodiment of the present invention.

Fig. 2 is a partial sectional view showing a part of a section along line II-II of fig. 1.

Fig. 3 is a partial sectional view showing a part of a section taken along the line III-III of fig. 2.

Fig. 4 is a partial sectional view showing a part of a section along line IV-IV of fig. 2.

Fig. 5 is a partial cross-sectional view of a portion corresponding to fig. 3 of a modification of the steering device according to the embodiment of the present invention.

Fig. 6 is a partial cross-sectional view of a portion corresponding to fig. 4 of a modification of the steering device according to the embodiment of the present invention.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

A steering device 100 according to an embodiment of the present invention will be described with reference to fig. 1 and 2. Fig. 1 is a structural view of a steering device 100, and fig. 2 is a partial sectional view showing a part of a section taken along line II-II of fig. 1.

The steering device 100 is mounted on a vehicle, and is a device that converts steering torque applied to a steering wheel 10 by a driver to change the direction of a vehicle wheel 1. Hereinafter, a case where the steering device 100 is an electric power steering device having a function of assisting a steering force will be described.

As shown in fig. 1, the steering device 100 includes: a steering shaft 20 that is rotated by a steering torque input from the steering wheel 10; the rack shaft 30 as a steering shaft changes the direction of the wheels 1 in accordance with the rotation of the steering shaft 20.

The steering shaft 20 is composed of an input shaft 21 that rotates in accordance with a steering operation performed by a driver to operate the steering wheel 10, an output shaft 22 that displaces a rack shaft 30, and a torsion bar 23 that couples the input shaft 21 and the output shaft 22.

The rack shaft 30 is a shaft-like member provided to extend in the lateral direction of the vehicle, and the rack shaft 30 is coupled to one wheel 1 via a first tie rod (tie rod)41a and a first knuckle arm (knuckle arm)42a, and is coupled to the other wheel 1 via a second tie rod 41b and a second knuckle arm 42 b.

The first and

second tie rods

41a and 41b are connected to the rack shaft 30 so as to be swingable via first and second

spherical joints

43a and 43b, which are connection parts provided at both ends of the rack shaft 30. The coupling portion that couples the rack shaft 30 to the first and

second tie rods

41a and 41b is not limited to the first and

second ball joints

43a and 43b, and other types of universal joints may be used.

The output shaft 22 and the rack shaft 30 are coupled to each other via a rack-and-pinion mechanism including a pinion gear 22a provided at an end portion of the output shaft 22 and a rack gear 30a provided at the rack shaft 30. The pinion gear 22a and the rack gear 30a mesh with each other, and the torque of the output shaft 22 is converted into a load in the axis O1 direction of the rack shaft 30 via the pinion gear 22a and the rack gear 30a, and is transmitted to the rack shaft 30. Thereby, the rack shaft 30 is displaced in the axis O1 direction by the transmitted torque, and the direction of the wheel 1 is changed via the first tie rod 41a and the second tie rod 41 b.

Further, the steering device 100 includes: an electric motor 50 driven to assist a steering force in accordance with a steering operation; and a speed reducer 52 that reduces the speed of rotation of the electric motor 50 and transmits the rotation to the steering shaft 20.

The speed reduction unit 52 is a worm gear mechanism including a worm shaft 53 driven by the electric motor 50 and a worm wheel 54 provided on the output shaft 22. The worm shaft 53 and the worm wheel 54 are meshed with each other, and the torque of the electric motor 50 is transmitted to the output shaft 22 via the worm shaft 53 and the worm wheel 54. The torque transmitted from the electric motor 50 to the output shaft 22 is further transmitted to the rack shaft 30 via the pinion gear 22a and the rack shaft 30 a.

Further, the steering device 100 includes: a torque sensor 62 that detects a torque acting on the torsion bar 23; and a controller 60 that controls driving of the electric motor 50 based on a detection value of the torque sensor 62.

The controller 60 is constituted by a microcomputer including: a CPU (Central Processing Unit) for performing arithmetic Processing; a ROM (Read-Only Memory) that stores a control program and the like executed by the CPU; a RAM (random access memory) for storing the operation result of the CPU and the like. The controller 60 may be constituted by a single microcomputer or a plurality of microcomputers.

The torque sensor 62 detects a steering torque applied to the input shaft 21 in accordance with a steering operation performed by the driver, and outputs a voltage signal corresponding to the detected steering torque to the controller 60. The controller 60 calculates the torque output from the electric motor 50 based on the voltage signal from the torque sensor 62, and controls the driving of the electric motor 50 so that the torque is generated.

In this way, in the steering device 100 configured as described above, the steering torque applied to the input shaft 21 can be detected by the torque sensor 62, and the controller 60 controls the driving of the electric motor 50 based on the detection result, thereby assisting the steering operation of the driver.

As shown in fig. 2, the steering device 100 further includes: a rack housing 31 as a housing that houses the rack shaft 30; a first bush 35 and a second bush 36 which are provided in the rack housing 31 and slidably support the rack shaft 30; a pressing mechanism 38 that presses the rack shaft 30 toward the pinion 22 a; and a first cover 37a and a second cover 37b that cover the first ball joint 43a and the second ball joint 43b that connect the rack shaft 30 and the first tie rod 41a and the second tie rod 42 b.

The rack housing 31 is a cylindrical member formed so as to penetrate a first housing hole 31a for housing the rack shaft 30. In the rack housing 31, a second housing hole 31b and a third housing hole 31c are further formed, wherein the second housing hole 31b is formed in a direction intersecting the first housing hole 31a and houses the pinion gear 22 a; the third housing hole 31c is formed on the opposite side of the meshing portion between the pinion gear 22a and the rack gear 30a with the axis O1 of the rack shaft 30 interposed therebetween, and houses the pressing mechanism 38.

A first assembly hole 32 into which a first bush 35 is assembled is provided at one end of the first housing hole 31a, and a second assembly hole 33 into which a second bush 36 is assembled is provided at the other end of the first housing hole 31 a. The first assembly hole 32 has an annular groove 32a for retaining and positioning the first bush 35, and the second assembly hole 33 has an annular groove 33a for retaining and positioning the second bush 36.

The end surface of the first assembly hole 32 that opens is a first regulation surface 31d that comes into contact with the first spherical joint 43a coupled to the rack shaft 30, and the end surface of the second assembly hole 33 that opens is a second regulation surface 31e that comes into contact with the second spherical joint 43b coupled to the rack shaft 30. Therefore, the rack shaft 30 is restricted from moving in the axial direction by the first and

second ball joints

43a and 43b coming into contact with the first and second

restricting surfaces

31d and 31e provided on the rack housing 31.

The first sheath 37a and the second sheath 37b are each a meandering member formed of rubber or resin (elastic body). One end of the first sheath 37a is fastened to the end of the rack housing 31 and the other end is fastened to the first tie rod 41a, and the first sheath 37a covers the first ball joint 43a that couples the rack shaft 30 and the first tie rod 41a, one end of the second sheath 37b is fastened to the end of the rack housing 31 and the other end is fastened to the second tie rod 41b, and the second sheath 37b covers the second ball joint 43b that couples the rack shaft 30 and the second tie rod 41 b.

By providing the first sheath 37a and the second sheath 37b in this manner, water and foreign matter can be prevented from entering the rack housing 31. Further, by providing the first and

second sheaths

37a and 37b, it is possible to prevent the first and second

spherical joints

43a and 43b from being bitten by foreign matter or the like while maintaining lubricity of the first and second

spherical joints

43a and 43 b.

The pressing mechanism 38 includes: a pressure pad 38a that is in sliding contact with the rack shaft 30; an adjuster 38b screwed to the rack housing 31; and a spring 38c interposed between the pressure pad 38a and the regulator 38b in a compressed state, and biasing the pressure pad 38a toward the pinion 22 a.

By changing the screwing position of the adjuster 38b, the fixing load of the spring 38c is adjusted, and the force with which the rack shaft 30 is pressed against the pinion 22a changes. By thus biasing the rack shaft 30 toward the pinion gear 22a, the backlash (backlash) between the rack gear 30a and the pinion gear 22a is reduced, and the tooth striking noise generated by the rotation of the pinion gear 22a when the rack shaft 30 reciprocates is reduced.

The first bush 35 is a cylindrical member formed of resin, and includes a cylindrical main body portion 35a and a flange-like stopper portion 35b formed to protrude radially outward from one end of the main body portion 35 a. The first bush 35 is fixed to the rack housing 31 by fitting the retaining portion 35b into the annular groove 32a formed in the first assembly hole 32.

The second bush 36 has the same shape as the first bush 35, and is fixed to the rack housing 31 by fitting the retaining portion 36b into the annular groove 33a formed in the second assembly hole 33.

As shown in fig. 2, the rack shaft 30 slidably supported by the first bush 35 and the second bush 36 having the above-described shapes includes: a gear portion 30b provided with a rack gear 30 a; and a first cylindrical portion 30c and a second cylindrical portion 30d provided at both ends of the gear portion 30b, the first cylindrical portion 30c and the gear portion 30b adjacent to the first cylindrical portion 30c being slidably supported by a first bushing 35, and the second cylindrical portion 30d and the gear portion 30b adjacent to the second cylindrical portion 30d being slidably supported by a second bushing 36.

Here, since grease and lubricating oil are present between the rack housing 31 and the first and

second bushings

35, 36, and between the rack shaft 30 and the first and

second bushings

35, 36, there is almost no gap through which air can flow. Therefore, the space inside the first sheath 37a and the second sheath 37b is substantially sealed.

When air cannot enter and exit the space inside the first and

second sheaths

37a and 37b, for example, even if the first and

second sheaths

37a and 37b expand in accordance with the reciprocating movement of the rack shaft 30, air does not flow into the first and

second sheaths

37a and 37b, and therefore the first and

second sheaths

37a and 37b may be recessed radially inward and may come into contact with the first and

second ball joints

43a and 43 b.

Further, when air cannot enter and exit the space inside the first sheath 37a and the second sheath 37b, for example, even if the first sheath 37a and the second sheath 37b contract in accordance with the reciprocating movement of the rack shaft 30, air does not flow out from inside the first sheath 37a and the second sheath 37b, and therefore, the first sheath 37a and the second sheath 37b may bulge radially outward and contact with the members disposed in the periphery.

As described above, when contact with other components and extreme deformation are repeated, eventually the first sheath 37a and the second sheath 37b are broken, and intrusion of water or the like into the rack housing 31 cannot be prevented, and as a result, the steering device 100 may not be able to operate normally.

In addition, in a Vehicle having a relatively narrow Vehicle width, for example, an All Terrain Vehicle (ATV) or a utility four-wheel Vehicle (SSV) capable of traveling over various terrains including rough terrains, since the length of the rack housing 31 in the Vehicle width direction is relatively short, the first bushing 35 and the second bushing 36 support not only the first cylindrical portion 30c and the second cylindrical portion 30d of the rack shaft 30 but also the gear portion 30 b.

When the first and

second bushings

35, 36 support the first and second

cylindrical portions

30c, 30d, the spaces in the first and

second sheaths

37a, 37b are in a substantially sealed state, while when the first and

second bushings

35, 36 support the gear portion 30b, the spaces in the first and

second sheaths

37a, 37b are in a state of communication with the space in the first housing hole 31 a.

When the space in the first sheath 37a and the second sheath 37b is switched from the sealed state to the state of communicating with the space in the first housing hole 31a, air flows into and out of the space in the first sheath 37a and the second sheath 37 b. Therefore, the first sheath 37a and the second sheath 37b may be rapidly deformed, and a sound in which air rapidly flows may be generated as an abnormal sound.

In the present embodiment, in order to avoid the above phenomenon, the space in the first sheath 37a and the space in the second sheath 37b are always communicated with each other, and air can be made to flow between the space in the first sheath 37a and the space in the second sheath 37 b.

Next, a structure for communicating the space in the first sheath 37a and the space in the second sheath 37b will be described with reference to fig. 3 and 4. Fig. 3 is a partial sectional view showing a part of a section taken along the line III-III of fig. 2, and fig. 4 is a partial sectional view showing a part of a section taken along the line IV-IV of fig. 2.

As shown in fig. 3, the first bush 35 includes, in addition to the above-described retaining portion 35 b: a protrusion 35c provided to protrude radially outward from the stopper 35 b; and a slit 35d provided on the opposite side of the projection 35c with the axis O1 therebetween.

The slit 35d is a spiral cut formed along the entire length of the first bush 35, and is provided to reduce the outer diameter of the first bush 35 when the first bush 35 is assembled to the rack housing 31.

Since the contact area with the rack shaft 30 is reduced by the area of the slit 35d at the portion where the slit 35d is provided, the surface pressure is increased. Therefore, since the first bush 35 may be damaged when a large load acts on the portion, the protrusion 35c is provided in order to perform positioning of the first bush 35 in the circumferential direction so that the portion provided with the slit 35d is arranged at a predetermined position, for example, a position where a relatively small load acts. In other words, the protrusion 35c is provided to prevent the first bush 35 from rotating about the axial center O1.

On the other hand, in the first assembly hole 32 of the rack housing 31, a restriction groove 32b into which the protrusion 35c is inserted is formed. The regulating groove 32b is a groove having a bottom surface 32c and side surfaces 32d facing each other, and is formed on the inner peripheral surface of the first assembly hole 32 along the axial center O1 of the rack shaft 30.

When the protruding portion 35c of the first bush 35 is inserted into the restricting groove 32b, the movement of the protruding portion 35c in the circumferential direction is restricted by the side surface 32d of the restricting groove 32 b. As a result, the first bush 35 is restricted from rotating about the axial center O1, and the portion where the slit 35d is provided is maintained in a state of being arranged at a predetermined position.

In general, when the vehicle travels, the rack shaft 30 is pressed against the rack housing 31 toward the upper and lower sides in the vertical direction by the vibration during traveling. Therefore, the positional relationship between the regulating groove 32b and the projecting portion 35c is set so that the portion where the slit 35d is provided is arranged to avoid the upper and lower portions in the vertical direction.

The regulating groove 32b is opened in the first regulating surface 31d, and a first length L1 is set to be longer than a second length L2, the first length L1 being the length of the regulating groove 32b in the axial center O1 direction of the rack shaft 30 from the first regulating surface 31d as the opened end surface, and the second length L2 being the length from the first regulating surface 31d to the insertion tip end surface 35e of the first bush 35 assembled in the first assembling hole 32.

Therefore, the restriction groove 32b opens into the first accommodation hole 31a at a portion closer to the center of the rack housing 31 than the portion where the first bush 35 is provided. In other words, the restriction groove 32b is in a state of communicating with the space in the first housing hole 31a so as not to be blocked by the first bush 35.

As shown in fig. 3, third length L3 is formed to be longer than fourth length L4 such that a passage through which air can flow is formed between bottom surface 32c and protruding portion 35c, third length L3 being the length from axial center O1 of rack shaft 30 to bottom surface 32c of regulating groove 32b, and fourth length L4 being the length from axial center O1 of rack shaft 30 to the tip end of protruding portion 35 c.

Since the restriction groove 32b is formed in this way, the space faced by the first restriction surface 31d, that is, the space in the first sheath 37a is always communicated with the space in the first housing hole 31a via the passage formed between the bottom surface 32c and the protrusion 35c and the restriction groove 32b formed to extend further than the insertion tip end surface 35e of the first bush 35.

Further, since the bottom surface 32c of the regulating groove 32b is not in contact with any member, in the case of manufacturing the rack housing 31 by casting, the bottom surface 32c may be the same as the surface of the casting. In this case, the bottom surface 32c is not parallel to the axial center O1, but is formed slightly inclined with respect to the axial center O1 according to the notch gradient.

On the other hand, a restriction groove (not shown) similar to the restriction groove 32b is also formed in the second assembly hole 33 into which the second bush 36 is assembled. Therefore, the space in the second sheath 37b is also always in communication with the space in the first housing hole 31a via the regulating groove formed in the second assembly hole 33.

As a result, the space in the first cover 37a and the space in the second cover 37b are always in communication with each other via the space in the first housing hole 31 a.

Therefore, for example, in fig. 2, when the rack shaft 30 moves rightward, the first sheath 37a expands, and the second sheath 37b contracts, air in the space inside the second sheath 37b after contraction flows into the space inside the first sheath 37a after expansion through the space inside the first housing hole 31 a. Therefore, the first sheath 37a is prevented from being recessed radially inward, or the second sheath 37b is prevented from being raised radially outward, and as a result, the first sheath 37a and the second sheath 37b can be prevented from being damaged.

Further, since the space in the first sheath 37a and the space in the second sheath 37b are always communicated with each other, even when the state is switched from the state in which the first and second

cylindrical portions

30c and 30d are supported by the first and

second bushings

35 and 36 to the state in which the gear portion 30b is supported by the first and

second bushings

35 and 36, the flow of air to the spaces in the first and

second sheaths

37a and 37b hardly changes. Therefore, the first sheath 37a and the second sheath 37b can be prevented from being rapidly deformed, and the generation of the sound of the air flow can be suppressed.

In the present embodiment, the size of the minimum passage cross-sectional area of the passage that communicates the space in the first sheath 37a and the space in the second sheath 37b is set in accordance with the flow path resistance of the air that is given to move between the space in the first sheath 37a and the space in the second sheath 37b so that the air can smoothly move between the space in the first sheath 37a and the space in the second sheath 37b in accordance with the reciprocating movement of the rack shaft 30.

Specifically, for example, when the cross-sectional area of the passage formed between the bottom surface 32c and the protruding portion 35c is the smallest, the length of the second length L3 is set so that the magnitude of the flow path resistance given to the flow of air when the maximum flow rate of air flows in this portion becomes equal to or smaller than a predetermined value. For example, the larger the difference between the length of the third length L3 and the length of the third length L4, the larger the cross-sectional area of the passage formed between the bottom surface 32c and the protrusion 35c, the smaller the flow path resistance. That is, the flow path resistance can be reduced as the length of the third length L3 is relatively longer than the length of the fourth length L4. However, the length of the third length L3 is limited by the size of the wall thickness of the rack housing 31. Further, the flow path resistance can be reduced as the length of the fourth length L4 is relatively shorter than the length of the third length L3. However, the length of the fourth length L4 is limited to a range in which the protruding portion 35c can exert the rotation stop function.

For example, when the cross-sectional area of the passage formed between the insertion tip end surface 35e and the restriction groove 32b is the smallest, the length of the first length L1 is set so that the magnitude of the flow path resistance given to the flow of air when the maximum flow rate of air flows in this portion becomes equal to or less than a predetermined value. Since the flow path resistance can be reduced as the first length L1 is increased, the length of the first length L1 is limited by the positions and sizes of the second receiving hole 31b and the third receiving hole 31c formed in the rack housing 31.

The predetermined value of the flow path resistance is experimentally set in consideration of the deformation state of each of the

sheaths

37a and 37 b. Specifically, the amount of deformation of each

sheath

37a, 37b radially outward and radially inward when the rack shaft 30 is moved at the maximum speed is measured so as to change the flow path resistance, and the flow path resistance when the measured amount of deformation is within the allowable range is set as a predetermined value.

In this way, by appropriately setting the size of the minimum passage cross-sectional area of the passage that connects the space in the first sheath 37a and the space in the second sheath 37b, specifically, the size of the minimum passage cross-sectional area of the passage formed between the first bush 35 and the regulating groove 32b and the passage formed between the second bush 36 and the regulating groove, it is possible to reliably suppress deformation of the

sheaths

37a, 37 b.

According to the above embodiment, the following effects are obtained.

In the steering device 100, the space in the first sheath 37a and the space in the second sheath 37b are always communicated with each other via the regulating groove 32b provided in the rack housing 31 for regulating the rotation of the

bushes

35 and 36. By allowing the space in the first sheath 37a and the space in the second sheath 37b to constantly communicate with each other by the regulating groove 32b in this manner, air is allowed to move between the two

sheaths

37a, 37b, and it is possible to suppress the

sheaths

37a, 37b from being deformed extremely when the spaces in the

sheaths

37a, 37b expand and contract in accordance with the reciprocating movement of the rack shaft 30.

Next, a modified example of the above embodiment will be described.

In the above embodiment, two

bushes

35, 36 that slidably support the rack shaft 30 are provided. Alternatively, the number of bushings may be only one.

In the above embodiment, the steered shaft is the rack shaft 30 having the rack gear 30 a. The steered shaft is not limited to the rack shaft 30, and the rack gear 30a may not be provided if it is a shaft-like member to which steering force for changing the direction of the wheels 1 is transmitted via some transmission mechanism.

In the above embodiment, the protrusion 35c is formed on the first bush 35 and the second bush 36, and the regulation groove 32b into which the protrusion 35c is inserted may be formed in the first assembly hole 32 of the rack housing 31. Alternatively, as shown in fig. 5 and 6, the protrusion 132b may be formed on the rack housing 31 side, and the regulation groove 135c may be formed on the first bushing 135 and the second bushing 136 side. The following describes modifications shown in fig. 5 and 6. Fig. 5 is a view showing a cross section corresponding to the cross section shown in fig. 3, and fig. 6 is a view showing a cross section corresponding to the cross section shown in fig. 4.

The first bush 135 in this modification is a cylindrical member formed of resin, and includes a cylindrical main body 135a and a flange-shaped stopper 135b formed to protrude radially outward from one end of the main body 135 a. The first bush 135 is fitted into the retaining groove 132a of the first assembly hole 132 formed at one end of the first housing hole 31a by the retaining portion 135b, and is fixed to the rack housing 31.

The first bushing 135 includes, in addition to the retaining portion 135b, the following: a restriction groove 135c into which the protrusion 132b provided in the escape prevention groove 132a is inserted; and a slit 135d provided on the opposite side of the restriction groove 135c with the axis O1 therebetween. The regulating groove 135c is a groove formed in the main body 135a and the stopper 135b along the axial center O1 of the rack shaft 30, and is provided over the entire length of the first bush 135.

The protrusion 132b is a protrusion formed to protrude from the bottom surface of the slip-off preventing groove 132a toward the axial center O1, and the tip end surface of the protrusion 132b is formed to be flush with the inner circumferential surface of the first assembly hole 132. In other words, as shown in fig. 5, the separation preventing groove 132a is formed in a C-shape in a cross-sectional view so that a portion to be the protrusion 132b remains.

When the projection 132b formed in this way is inserted into the restriction groove 135c of the first bush 135, the side surface 135f of the restriction groove 135c abuts against the projection 132b, and the first bush 135 is restricted from rotating about the axial center O1. Further, the rotation of the first bushing 135 is restricted, so that the portion where the slit 135d is provided is maintained in a state of being arranged at a predetermined position.

As shown in fig. 6, a fifth length L5 is set to be longer than a sixth length L6, wherein the fifth length L5 is the length of the first assembly hole 132 in the axial center O1 direction of the rack shaft 30 from the first regulation surface 31d, which is the opening end surface of the first assembly hole 132, and the sixth length L6 is the length from the first regulation surface 31d to the insertion tip end surface 135e of the first bush 135 assembled in the first assembly hole 132. Therefore, the restriction groove 135c formed so as to reach the insertion tip end surface 135e is in a state of communicating with the space in the first accommodation hole 31a so as not to be blocked by the rack housing 31.

As shown in fig. 5, eighth length L8 is formed shorter than seventh length L7 such that a passage through which air can flow is formed between the bottom surface of regulation groove 135c and projection 132b, eighth length L8 being the length from axial center O1 of rack shaft 30 to the bottom surface of regulation groove 135c, and seventh length L7 being the length from axial center O1 of rack shaft 30 to the tip end of projection 132 b.

Since the restriction groove 135c is formed in this way, the space facing the first restriction surface 31d, that is, the space in the first sheath 37a is always communicated with the space in the first housing hole 31a via the passage formed between the bottom surface of the restriction groove 135c and the protrusion 132b and the passage formed between the restriction groove 135c and the first assembly hole 132.

On the other hand, the second bush 136, not shown, and the second assembly hole 133, not shown, to which the second bush 136, not shown, is assembled are also formed in the same shape. Therefore, the space in the second sheath 37b is also always in communication with the space in the first housing hole 31a via the regulating groove formed in the second bush 136.

As a result, in this modification as well, since the space in the first sheath 37a and the space in the second sheath 37b are always in communication with each other via the space in the first housing hole 31a, the same effect as that of the above-described embodiment can be obtained.

In the present embodiment, in order to smoothly move air between the space in the first sheath 37a and the space in the second sheath 37b in accordance with the reciprocating movement of the rack shaft 30, the minimum passage cross-sectional area of the passage that communicates the space in the first sheath 37a and the space in the second sheath 37b is set in accordance with the flow path resistance of the air that is applied to the space in the first sheath 37a and the space in the second sheath 37 b.

In the modification described above, although the restriction groove 135c is formed in the body portion 135a and the retaining portion 135b along the axial center O1 of the rack shaft 30, even when the restriction groove 135c is formed only in the retaining portion 135b, if air can move between the two

sheaths

37a, 37b through the restriction groove 135c, the restriction groove 135c may not be formed in the body portion 135 a. In addition, in the case where the restriction groove 135c is formed only in the retaining portion 135b, since the minimum passage cross-sectional area of the passage that connects the space in the first sheath 37a and the space in the first housing hole 31a may be small, in order to set the minimum passage cross-sectional area of the passage to a sufficient size, a groove that connects the restriction groove 135c formed in the retaining portion 135b and the space in the first housing hole 31a, and a groove that connects the restriction groove 135c formed in the retaining portion 135b and the space in the first sheath 37a may be formed on the inner peripheral surface of the first assembly hole 132.

In addition, the above-described embodiment and the above-described modified example may be combined to provide a protruding portion on one of the first bush and the second bush and a restriction groove on the other.

Hereinafter, the structure, operation, and effects of the embodiments of the present invention will be summarized.

The steering device 100 includes: a rack shaft 30 that changes the direction of the wheels 1 by transmitting a steering force; a rack housing 31 that houses the rack shaft 30; first and

second bushings

35, 135, 36, 136 that are provided in the rack housing 31 and slidably support the rack shaft 30; a first pull rod 41a and a second pull rod 41b coupled to the rack shaft 30 so as to be swingable; a first sheath 37a provided in the rack housing 31 and covering a coupling portion between the rack shaft 30 and the first tie rod 41 a; and a second sheath 37b provided in the rack housing 31 and covering a coupling portion between the rack shaft 30 and the second tie rod 41b, wherein one of the

first bushings

35, 135, the second bushings 36, 136, and the rack housing 31 is formed with protruding

portions

35c, 132b protruding toward the other, the other is formed with restricting

grooves

32b, 135c into which the protruding

portions

35c, 132b are inserted in the axial direction of the rack shaft 30, and a space in the first sheath 37a and a space in the second sheath 37b are always communicated with each other via the restricting

grooves

32b, 135 c.

In this configuration, the space in the first sleeve 37a and the space in the second sleeve 37b are always communicated with each other via the regulating

grooves

32b and 135c provided to regulate the rotation of the

bushes

35 and 36. By allowing the space in the first sheath 37a and the space in the second sheath 37b to constantly communicate with each other by the regulating

grooves

32b and 135c in this manner, air is allowed to move between the two

sheaths

37a and 37b, and it is possible to suppress the

sheaths

37a and 37b from being deformed extremely when the spaces in the

sheaths

37a and 37b expand and contract in accordance with the reciprocating movement of the rack shaft 30.

The protrusion 35c is formed on the first bush 35 and the second bush 36, the regulation groove 32b is formed on the rack housing 31, the rack housing 31 has a first regulation surface 31d and a second regulation surface 31e as opening end surfaces where the regulation groove 32b opens in the axis O1 direction of the rack shaft 30, and the first length L1 is set longer than the second length L2, the first length L1 is the length of the regulation groove 32b in the axis O1 direction, and the second length L2 is the length between the insertion tip end surface 35e of the first bush 35 and the second bush 36 inserted into the rack housing 31 and the first regulation surface 31d and the second regulation surface 31 e.

In this configuration, a first length L1 is set to be longer than a second length L2, the first length L1 being the length of the regulating groove 32b in the axial center O1 direction of the rack shaft 30 from the first regulating surface 31d and the second regulating surface 31e, which are the open end surfaces, and the second length L2 being the length from the first regulating surface 31d and the second regulating surface 31e to the insertion tip end surface 35e of the first bush 35 and the second bush 36 assembled in the first assembly hole 32 and the second assembly hole 33. Therefore, the regulating groove 32b is opened in the first housing hole 31a at a portion closer to the center of the rack housing 31 than the portion where the first bush 35 and the second bush 36 are provided, and is in a state of always communicating with the space in the first housing hole 31 a. By forming the regulating groove 32b in this manner, the space in the first sheath 37a and the space in the second sheath 37b can be always communicated with each other via the space in the first housing hole 31 a.

The first bush 35 and the second bush 36 include: a cylindrical main body 35 a; and a retaining portion 35b formed to protrude radially outward from the main body portion 35a and engaged with the rack housing 31, and a protruding portion 35c formed to protrude radially outward from the retaining portion 35 b.

In this configuration, the protrusion 35c provided to regulate the rotation of the first bush 35 and the second bush 36 is formed to protrude radially outward from the stopper 35 b. By thus configuring not to separately form the protrusion 35c from the stopper 35b but to continuously form the protrusion 35c on the stopper 35b, the shapes of the first bush 35 and the second bush 36 are simplified, and the manufacturing cost of the first bush 35 and the second bush 36 can be reduced.

The protrusion 132b is formed in the rack housing 31, the regulation groove 135c is formed in the first bush 135 and the second bush 136, the rack housing 31 has a first regulation surface 31d and a second regulation surface 31e as opening end surfaces in which the first assembly hole 132 and the second assembly hole 133 assembled with the first bush 35 and the second bush 136 are opened in the axis O1 direction of the rack shaft 30, and a fifth length L5 is set longer than a sixth length L6, the fifth length L5 is the length of the first assembly hole 132 and the second assembly hole 133 in the axis O1 direction, and the sixth length L6 is the length between the insertion tip end surface 135e of the first bush 135 and the second bush 136 inserted into the rack housing 31 and the first regulation surface 31d and the second regulation surface 31 e.

In this configuration, a fifth length L5 is set to be longer than a sixth length L6, L5 being the length of the first and second assembly holes 132, 133 in the axial center O1 direction of the rack shaft 30 from the first and

second regulating surfaces

31d, 31e, which are open end surfaces, and L6 being the length from the first and

second regulating surfaces

31d, 31e to the insertion tip end surface 135e of the first and second bushings 135, 136 assembled in the first and second assembly holes 132, 133. Therefore, the restriction groove 135c is formed so as to be opened in the first housing hole 31a without being blocked by the rack housing 31 and to be in a state of being constantly communicated with the space in the first housing hole 31a, and thus the space in the first sheath 37a and the space in the second sheath 37b can be constantly communicated with each other through the space in the first housing hole 31 a.

The first bushing 135 and the second bushing 136 have: a cylindrical main body 135 a; and a retaining portion 135b formed to protrude radially outward from the main body portion 135a and engaged with the rack housing 31, and a regulating groove 135c is formed in the main body portion 135a and the retaining portion 135 b.

In this configuration, the restricting groove 135c provided to restrict the rotation of the first bushing 135 and the second bushing 136 is formed in the main body 135a and the stopper 135 b. By forming the restricting groove 135c over the entire length of the first and second bushings 135 and 136 without forming it in a part of the first and second bushings 135 and 136, the shapes of the first and second bushings 135 and 136 can be simplified, and the manufacturing cost of the first and second bushings 135 and 136 can be reduced.

The cross-sectional area of the passage formed by the

restriction grooves

32b and 135c and connecting the space in the first sheath 37a and the space in the second sheath 37b is set according to the flow path resistance given to the air moving between the space in the first sheath 37a and the space in the second sheath 37b according to the reciprocating movement of the rack shaft 30.

In this configuration, the size of the cross-sectional area of the passage formed by the restricting

grooves

32b, 135c is set according to the flow path resistance given to the air moving between the space in the first sheath 37a and the space in the second sheath 37 b. By setting the size of the cross-sectional area of the passage so that the flow path resistance given to the air moving between the space in the first sheath 37a and the space in the second sheath 37b is smaller than a predetermined value, the air can smoothly go back and forth between the space in the first sheath 37a and the space in the second sheath 37 b. By smoothly returning air between the space in the first sheath 37a and the space in the second sheath 37b in this way, it is possible to reliably suppress the

sheaths

37a and 37b from being deformed extremely.

At least a part of the surface constituting the regulating groove 32b is a casting surface.

In this structure, at least a part of the surface constituting the regulating groove 32b is a casting surface. By thus forming a part of the regulating groove 32b as it is on the surface of the casting, the cutting process required to form the regulating groove 32b can be eliminated to reduce the machining cost, and as a result, the manufacturing cost of the steering apparatus 100 can be reduced.

The

first bushings

35, 135 and the second bushings 36, 136 are made of resin.

In this structure, the

first bushings

35, 135 and the second bushings 36, 136 are formed of resin. Therefore, the weight of the

first bushings

35, 135 and the second bushings 36, 136 is reduced as compared with the case where the

first bushings

35, 135 and the second bushings 36, 136 are made of metal. As a result, the weight of the steering device 100 can be reduced.

Although the embodiments of the present invention have been described above, the above embodiments are merely some of application examples of the present invention, and the technical scope of the present invention is not limited to the specific configurations of the above embodiments.

The application claims priority based on Japanese patent application 2019-130500, filed on 12.7.2019 with the office, and the entire content of which is incorporated by reference in the present specification.

Claims

1. A steering device is provided with:

a steering shaft that changes a direction of a wheel by being transmitted with a steering force;

a housing that houses the steered shaft;

a bush provided in the housing and supporting the steering shaft to be slidable;

a first link and a second link that are connected to the steered shaft so as to be able to freely swing;

a first sheath that is provided in the housing and covers a coupling portion between the steered shaft and the first link;

a second sheath that is provided in the housing and covers a connection portion between the steered shaft and the second link,

a protruding portion protruding toward the other is formed on either one of the bush and the housing, and a restricting groove into which the protruding portion is inserted is formed on the other in an axial direction of the steered shaft,

the space in the first sheath and the space in the second sheath are always communicated via the restriction groove.

2. The steering apparatus according to claim 1,

the protrusion is formed at the bushing, the restriction groove is formed at the outer case,

the housing has an open end surface of the restricting groove that opens in the axial direction of the steered shaft,

the length of the restriction groove in the axial direction is longer than the length between the insertion tip end surface and the opening end surface of the bush inserted into the housing.

3. The steering apparatus according to claim 2,

the bushing has:

a cylindrical body portion;

a retaining portion formed to protrude radially outward from the main body portion and locked to the housing,

the protrusion is formed to protrude radially outward from the retaining portion.

4. The steering apparatus according to claim 1,

the protrusion is formed at the housing, the restriction groove is formed at the bushing,

the housing has an open end face in which an assembly hole into which the bush is assembled is open in an axial direction of the steered shaft,

the length of the assembly hole in the axial direction is longer than the length between the insertion tip end surface and the opening end surface of the bush inserted into the housing.

5. The steering apparatus according to claim 4,

the bushing has:

a cylindrical body portion;

the restriction groove is formed in the body portion and the coming-off prevention portion.

6. The steering apparatus according to claim 1,

the cross-sectional area of the passage formed by the restriction groove and communicating the space inside the first sheath and the space inside the second sheath is set according to a resistance given to the air moving between the space inside the first sheath and the space inside the second sheath according to the reciprocating movement of the steered shaft.